The present application relates generally to integrated circuits, and more specifically to a charge pump circuit providing a constant output current.
Charge pump circuits are known that may be employed in integrated circuits to charge one or more circuit nodes to predetermined voltage levels. For example, a conventional charge pump circuit may include at least one current source, at least one switching element coupled between the current source and an output node, and a load capacitor coupled between the output node and ground potential. In a typical mode of operation, the switching element switches in response to an input signal to allow current pulses to flow from the current source through the output node. Further, the load capacitor operates as an integrator to convert the current pulses into an output voltage level.
One drawback of the conventional charge pump circuit is that as the output level increases the efficiency of the charge pump frequently decreases, which can manifest itself in a reduction in the charge rate of the charge pump over time. This is, at least in part, because the conventional charge pump is often incapable of delivering a constant output current. Such inefficiency can also make the conventional charge pump susceptible to, e.g., unwanted output leakage currents and limited output slew rates.
It would therefore be desirable to have an improved charge pump circuit that provides a constant output current and avoids the drawbacks of the above-described conventional charge pump circuit.